There are number of different forms of differential confocal microscopy. In one differential form, the Nomarski microscope measures one component of a conjugated quadratures of fields corresponding to the electrical interference signal of two images superimposed in an image plane. In another differential form, the conjugated quadratures of a dark field are measured one point at a time. In another differential form, the conjugated quadratures of each of two fields corresponding to two images superimposed in an image plane are measured one point at a time. In commonly owned U.S. Provisional Patent Application No. 60/447,254 (ZI-40) entitled “Transverse Differential Interferometric Confocal Microscopy” and U.S. patent application Ser. No. 10,778,371, filed Feb. 13, 2004 (ZI-40) also entitled “Transverse Differential Interferometric Confocal Microscopy” both of which are by Henry A. Hill, it is taught how to practice transverse differential interferometric confocal microscopy. In commonly owned U.S. Provisional Patent Application No. 60/448,360 (ZI-41) entitled “Longitudinal Differential Interferometric Confocal Microscopy” and U.S. patent application Ser. No. 10,782,057, filed Feb. 19, 2004 (ZI-41) also entitled “Longitudinal Differential Interferometric Confocal Microscopy” both of which are by Henry A. Hill, it is taught how to practice longitudinal differential interferometric confocal microscopy. The contents of both the cited U.S. Provisional Applications and the cited U.S. Patent Applications are herein incorporated in their entirety by reference.
However, neither the prior art nor the two cited U.S. provisional patent applications or the two cited U.S. Patent Applications teach how to practice differential interferometric confocal microscopy wherein an array of conjugated quadratures of fields are measured jointly, where the components of each conjugated quadratures may be measured jointly, and where each conjugated quadratures represent a difference of conjugated quadratures of fields of converging beams subsequently scattered/reflected or transmitted by a common location on a substrate surface wherein one of the converging beams subsequently scattered/reflected from the location is focused to an image plane located above the substrate surface and the second of the converging beams subsequently scattered/reflected from the location is focused to an image plane located below the substrate surface.
Also, prior art does not teach how to practice dark field differential interferometric confocal microscopy wherein an array of conjugated quadratures of fields are measured jointly, where the components of each conjugated quadratures may be measured jointly, where each conjugated quadratures represents a difference of conjugated quadratures of fields of converging beams subsequently scattered/reflected from a common location on a substrate surface wherein one of the converging beams subsequently scattered/reflected or transmitted by the location is focused to an image plane located above the substrate surface and the second of the converging beams subsequently scattered/reflected or transmitted by the location is focused to an image plane located below the substrate surface, and where the nominal values of the conjugated quadratures of the array of conjugated quadratures is zero, i.e., the field that is being measured is nominally dark.